In a series of tweets, Gremminger wrote: “I just flew into LGA and witnessed a United flight attendant instruct a passenger to put her dog bag in the overhead bin. It was clearly a dog and while the customer was adamant about leaving it under the seat, the attendant pushed her to do so.”

“Myself and a fellow passenger felt like that was NOT a thing. I am not a flight attendant tho. Maybe they have air ventilation in there that I didn’t know about. I tried googling rules about pets on board but didn’t have ample time before takeout.”

“At the end of the flight, the woman found her dog, deceased. She sat in the aeroplane aisle crying, and all of surrounding passengers were utterly stunned.”

“I am disgusted and traumatized. Pets are family. How could a trained flight attendant instruct a passenger to place her dog in that bin. It was her job to understand the plane and it’s rules/limitations.”

United Airlines have taken full responsibility for the incident.

A statement from the airline read: "We assume full responsibility for this tragedy and express our deepest condolences to the family and are committed to supporting them.”

"We are thoroughly investigating what occurred to prevent this from ever happening again. Pets should never be placed in the overhead bin.”